Sequential postnatal developmental studies of immature animal skeletons are rare. Similar studies in the human do not exist. This presents a large gap in our knowledge of chronological skeletal development during childhood, and renders the capacity to diagnose and treat many pediatric and orthopaedic diseases difficult because of this lack of basic data. The objective of this study will be to systematically obtain data on the longitudinal (chronological) development of the skeleton, from birth to skeletal maturity, in the human and selected animals. The comparative anatomy phase is essential to the derivation of appropriate animal models of human disease and deformity. The emphasis will be on gross morphology (with radiologic correlations), microscopic anatomy and biomechanics. In addition, the changing gross and microscopic aspects of the blood supply of the developing epiphysis (i.e., cartilage canals) will be assessed in detail. Finally, after obtaining appropriate normal data, several disease processes--particularly osteomyelitis, osteochondroma and congenital hip dysplasia--will be explored, both in human and appropriate animal models. The information obtained from the normal anatomical studies should form the basis for subsequent dynamic development studies of appropriate experimental animals that will adequately simulate normal human skeletal development and abnormal development as it applies to important clinical problems.